1. Field of the Invention
The present invention relates to an axial fan unit in which two or more fans are connected coaxially with each other.
2. Description of the Related Art
Electronic devices having frames, e.g., personal computers and servers, include cooling fans therein. The cooling fans are used for cooling electronic components inside the frames. When density of the electronic components inside the frames increases, concentration of heat generated by the electronic components occurs and lowers performances of the electronic components. In order to prevent this, cooling fans are required to have improved performances.
Among various types of electronic devices, relatively large sized electronic devices, e.g., servers larger than typical personal computers, require cooling fans which can achieve both a high static pressure and a large flow rate of air. One example of such cooling fans is an axial fan unit formed by at least two fans connected coaxially with each other. Japanese Unexamined Patent Publication No. 2004-278371 and its counter part U.S. Pat. No. 7,156,611 disclose a contra-rotating axial fan unit in which two impellers rotating in opposite directions to each other are coaxially arranged in a housing.